For silicon photomultiplier-based (SiPM) detectors, the temperature of the SiPM device can be one of the critical parameters affecting the detector's performance. Even with cooling systems, the actual temperature of a SiPM device can vary due to heat dissipation, non-uniform cooling, environmental changes, and other influences. The temperature variation can degrade detector timing and energy resolution.
One of the temperature effects degrading the timing resolution is a variation in the breakdown voltage and thus gain of the SiPM device. Additional jitter can be introduced by temperature variation in a detector implementing a leading edge discrimination (LED) method for timing measurement. The baseline fluctuation of the SiPM device's dark current can also limit both timing and energy resolution. For a conventional positron emission tomography imaging (PET) detector, a cooling system can reduce the dark noise contribution and stabilize the device temperature. However, conventional cooling systems rely on a thermocouple's indirect measurement of the SiPM microcell temperature by sensing the device's package temperature, which can limit its accuracy.
Real-time measurement and compensation of the temperature is not supported in conventional devices. Another conventional approach generally multiplexes the output signal of several pixels together, where accuracy is also limited by optical crosstalk. Therefore, this approach cannot take into consideration non-uniformity of each device either.